In Phase I, BIOTEK began development of an implant which will deliver levonorgestrel for at least one year, which will be implantable by trocar, which will be surgically removable before the end of drug delivery, and which will biodegrade and resorb if left in place after depletion. To achieve these goals, we have utilized a very high molecular weight poly-L-lactic acid, a member of a family of biodegradable polyesters already used in FDA-approved parenteral products. The implants. The implants tested have excellent strength properties and they release levonorgestrel at the desired rate in the first year. In Phase II, our objectives are to improve methods of manufacture, to prepare implants which limit levonorgestrel release to one year; to confirm the drug release and strength retention of the implants in vivo, and to obtain preclinical safety and stability data. PROPOSED COMMERCIAL APPLICATION: The most important potential benefit of the new formulation will be to make fertility regulation easier for women who are now using a levonorgestrel product or who would do so if such a product were silicone free and less traumatic. The new process could also be employed for other sustained delivery purposes, such as administration of estradiol for female hormone replacement therapy or administration of testosterone to hypogonadal men.